Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) segment $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) reporting_unit $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) shares	Feb. 10, 2020	Apr. 15, 2019
Property, Plant and Equipment [Line Items]
Number of operating segments | segment			2
Costs of sales		$ 174,461,000				$ 149,821,000	$ 163,727,000
Selling, general and administrative		46,196,000				38,068,000	35,810,000
Recorded inventory write-downs	$ 12,000,000.0	12,000,000.0	$ 12,000,000.0	$ 12,000,000.0	$ 12,000,000.0	10,200,000
Accumulated depreciation, and property plant, and equipment	19,864,000	19,864,000	19,864,000	19,864,000	19,864,000	17,858,000
Change in fair value of contingent consideration		3,340,000				0	450,000
Contingent consideration liability	0	0	0	0	0
Life insurance balance	3,700,000	3,700,000	3,700,000	3,700,000	3,700,000	3,700,000
Deferred compensation liability	$ 2,800,000	$ 2,800,000	$ 2,800,000	$ 2,800,000	$ 2,800,000	3,200,000
Long-term deferred amount due 2021	50.00%	50.00%	50.00%	50.00%	50.00%
Long-term deferred amount due 2022	50.00%	50.00%	50.00%	50.00%	50.00%
Accrued payroll taxes	$ 2,800,000	$ 2,800,000	$ 2,800,000	$ 2,800,000	$ 2,800,000
Accrued payroll taxes, current	$ 1,400,000	1,400,000	$ 1,400,000	$ 1,400,000	$ 1,400,000
Impairment of intangible assets		0				0
Impairment of capitalized software						700,000
Cost of acquired and internally developed software		19,252,000				13,372,000	12,412,000
Capitalized software costs		3,800,000				4,100,000
Amortization of capitalized software costs		6,700,000
Amortization of identifiable intangible assets		$ 1,163,000				156,000	22,000
Amortization of intangible asset						$ 100,000
Notes conversion (in dollars per share) | $ / shares	$ 46.4037	$ 46.4037	$ 46.4037	$ 46.4037	$ 46.4037	$ 30.8356
Conversion of shares converted (in shares) | shares				638,051,000		3,700,272,000
Number of segments			2		2
Impairment of long-lived assets		$ 0				$ 0	$ 0
Restricted Stock
Property, Plant and Equipment [Line Items]
Nonvested stock outstanding (in shares) | shares	61,000	61,000	61,000	61,000	61,000	149,000
weighted average granted | $ / shares	$ 25.62	$ 25.62	$ 25.62	$ 25.62	$ 25.62	$ 24.62
Other Noncurrent Liabilities
Property, Plant and Equipment [Line Items]
Accrued payroll taxes	$ 1,400,000	$ 1,400,000	$ 1,400,000	$ 1,400,000	$ 1,400,000
Convertible Senior Notes Due 2024 | Convertible Debt
Property, Plant and Equipment [Line Items]
Stated interest rate									4.50%
Convertible Senior Notes Due 2026 | Convertible Debt
Property, Plant and Equipment [Line Items]
Stated interest rate								2.875%
Employee Stock Option
Property, Plant and Equipment [Line Items]
Incremental shares excluded from computation of diluted earnings per share (in shares) | shares				956,627		383,000	750,000
Restricted Stock
Property, Plant and Equipment [Line Items]
Incremental shares excluded from computation of diluted earnings per share (in shares) | shares				426,632		67,000	0
Cost of sales - contracts
Property, Plant and Equipment [Line Items]
Amortization of identifiable intangible assets		6,200,000				$ 4,300,000
Internally developed software costs not meeting general release threshold
Property, Plant and Equipment [Line Items]
Cost of acquired and internally developed software		6,500,000				2,500,000
Minimum
Property, Plant and Equipment [Line Items]
Warranty period	12 months
Estimated useful lives	3 years
Estimated useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Warranty period	36 months
Estimated useful lives	25 years
Estimated useful life	5 years
AccSys LLC (Restaurant Magic)
Property, Plant and Equipment [Line Items]
Change in fair value of contingent consideration		3,300,000
Contingent consideration liability	$ 0	0	$ 0	$ 0	$ 0	3,300,000
Brink Software
Property, Plant and Equipment [Line Items]
Change in fair value of contingent consideration							$ 500,000
Revision of Prior Period, Reclassification, Adjustment
Property, Plant and Equipment [Line Items]
Selling, general and administrative						1,100,000	800,000
Recorded inventory write-downs						600,000
Accumulated depreciation, and property plant, and equipment						2,000,000.0
Change in fair value of contingent consideration							(500,000)
Product
Property, Plant and Equipment [Line Items]
Costs of sales		58,887,000				51,189,000	60,694,000
Product | Revision of Prior Period, Reclassification, Adjustment
Property, Plant and Equipment [Line Items]
Costs of sales						100,000
Service
Property, Plant and Equipment [Line Items]
Costs of sales		$ 49,933,000				40,389,000	43,051,000
Service | Revision of Prior Period, Reclassification, Adjustment
Property, Plant and Equipment [Line Items]
Costs of sales						$ 1,000,000.0	$ 900,000